Survival of various implant-supported prosthesis designs following 36 months of clinical function

BACKGROUND

The use of endosseous dental implants to replace natural teeth lost to trauma, dental caries, or periodontal disease has become a predictable form of prosthetic treatment since gaining popularity in the early 1980s. While numerous clinical studies have focused on the survival of implants, few address the survival of different prosthesis designs.

METHODS

Beginning in 1991, 882 prostheses supported by more than 2,900 implants (687 patients) were placed by the Department of Veterans Affairs Dental Implant Clinical Research Group (DICRG). These prostheses were divided into five research strata based on arch location. The recommended design for each stratum was: bar-supported overdenture (maxillary completely edentulous); screw-retained hybrid denture (mandibular completely edentulous); screw-retained fixed partial denture (mandibular and maxillary posterior partially edentulous); and cemented single crown (maxillary anterior single tooth). Alternative overdenture designs were utilized in the edentulous arches when the recommended prosthesis could not be fabricated. Prosthesis success rates for the research strata were calculated for an observation time of up to 36 months following prosthesis placement.

RESULTS

Success rates for the maxillary edentulous stratum ranged from 94.6% for the bar-retained overdenture supported by five to six fixtures to 81.8% for the cap-retained overdenture. The mandibular edentulous strata produced success rates of 98.1% for the fixed hybrid prosthesis to 91.7% for the cap-retained prosthesis. Success rates for maxillary and mandibular posterior fixed partial dentures were 94.3% and 92.6%, respectively, while the maxillary anterior single-tooth prosthesis yielded a success rate of 98.1% for the 36-month observation period.

CONCLUSIONS

The recommended prosthesis designs investigated in this study proved to be reliable, with encouraging success rates for an observation period of 36 months following placement.

Interaction of Leishmania mexicana promastigotes with the plasminogen-plasmin system

The binding of human plasminogen and plasmin to the promastigote form of Leishmania mexicana was investigated. L. mexicana was capable to bind both molecules, the binding being inhibited by epsilon-aminocaproic acid. Scatchard plot analysis revealed a dissociation constant (Kd) value of 2.4+/-0.8 microM and 0.9+/-0.1 x 10(4) binding sites per cell for plasminogen and a Kd value of 1.2+/-0.4 microM and 1.6+/-0.2 x 10(5) binding sites per cell for plasmin. C-terminal lysine residues are involved in plasminogen binding to cells, since carboxypeptidase B treatment reduced this binding by 34%. Ligand blotting analysis showed a group of proteins, with molecular masses between 105 and 115 kDa, capable to interact with plasminogen. Zymogram analysis showed that the protease activity acquired by L. mexicana, due to the interaction with either plasminogen or plasmin, comprises an important fraction of the total protease activity at pH 7.7. Plasminogen activation by tissue-type plasminogen activator (t-PA) was enhanced by the presence of L. mexicana promastigotes. These results raise the question whether the interaction of L. mexicana with components of the fibrinolytic system is involved in the virulence of the parasite.

Reactive oxygen species generated at mitochondrial complex III stabilize hypoxia-inducible factor-1alpha during hypoxia: a mechanism of O2 sensing

During hypoxia, hypoxia-inducible factor-1alpha (HIF-1alpha) is required for induction of a variety of genes including erythropoietin and vascular endothelial growth factor. Hypoxia increases mitochondrial reactive oxygen species (ROS) generation at Complex III, which causes accumulation of HIF-1alpha protein responsible for initiating expression of a luciferase reporter construct under the control of a hypoxic response element. This response is lost in cells depleted of mitochondrial DNA (rho(0) cells). Overexpression of catalase abolishes hypoxic response element-luciferase expression during hypoxia. Exogenous H(2)O(2) stabilizes HIF-1alpha protein during normoxia and activates luciferase expression in wild-type and rho(0) cells. Isolated mitochondria increase ROS generation during hypoxia, as does the bacterium Paracoccus denitrificans. These findings reveal that mitochondria-derived ROS are both required and sufficient to initiate HIF-1alpha stabilization during hypoxia.

Brown adipose tissue response to cafeteria diet-feeding involves induction of the UCP2 gene and is impaired in female rats as compared to males

Noradrenaline-dependent brown adipose tissue (BAT) thermogenesis is activated by the cold and excess energy intake, largely depends on the activity of the uncoupling protein 1 (UCP1), and is mediated mainly through the beta3-adrenoceptor (beta3-AR). We investigated the expression of ucp2, a gene that encodes a putative UCP1-like uncoupling protein, along with that of ucp1 and beta3-ar, in the interscapular BAT (IBAT) of male and female rats chronically fed a cafeteria diet. After 3 months on this diet, male rats attained a 34% excess body mass and showed IBAT hypertrophy and increased IBAT thermogenic potential, in terms of both UCP1 and UCP2 mRNA expression (both by 1.6-fold), UCP1 protein expression (by 1.75-fold) and GDP binding to IBAT mitochondria (by 2.2-fold); female rats attained a larger excess body weight (50%) and their IBAT, although hypertrophied, showed no signs of increased thermogenic potential per gram of tissue. Interestingly, the IBAT of female rats was already activated compared to males. Treatment of mouse brown adipocytes in primary culture with noradrenaline also triggered a dose-dependent increase of the levels of UCP1 mRNA and UCP2 mRNA. Retroregulatory down-regulation of the beta3-AR mRNA levels was found in the two models used. The results support a physiological role for UCP2, along with UCP1, in rodent BAT thermogenesis.

Overexpression of catalase in cytosolic or mitochondrial compartment protects HepG2 cells against oxidative injury

HepG2 cells were transfected with vectors containing human catalase cDNA and catalase cDNA with a mitochondrial leader sequence to allow comparison of the effectiveness of catalase overexpressed in the cytosolic or mitochondrial compartments to protect against oxidant-induced injury. Overexpression of catalase in cytosol and in mitochondria was confirmed by Western blot, and activity measurement and stable cell lines were established. The intracellular level of H(2)O(2) induced by exogenously added H(2)O(2) or antimycin A was lower in C33 cell lines overexpressing catalase in the cytosol and mC5 cell lines overexpressing catalase in the mitochondria as compared with Hp cell lines transfected with empty vector. Cell death caused by H(2)O(2), antimycin A, and menadione was considerably suppressed in both the mC5 and C33 cell lines. C33 and mC5 cells were also more resistant to apoptosis induced by H(2)O(2) and to the loss of mitochondrial membrane potential induced by H(2)O(2) and antimycin A. In view of the comparable protection by catalase overexpressed in the cytosol versus the mitochondria, catalase produced in both cellular compartments might act as a sink to decompose H(2)O(2) and move diffusable H(2)O(2) down its concentration gradient. The present study suggests that catalase in cytosol and catalase in mitochondria are capable of protecting HepG2 cells against cytotoxicity or apoptosis induced by oxidative stress.

cDNA and protein characterization of human MAGE-10

MAGE genes are frequently expressed in several types of human malignancy and code for antigens recognized by cytotoxic T lymphocytes. We have previously described a monoclonal antibody (MAb), named 6C1, that recognizes the MAGE-1 protein and cross-reacts with a 72-kDa protein present in lysates of melanoma cells such as MZ2-MEL. To identify this protein, we have screened an expression library prepared from MZ2-MEL cells. Several clones that encoded a protein recognized by antibody 6C1 contained a sequence identical to that of MAGE-10, another member of the MAGE-A gene family. Full-length MAGE-10 cDNA clones, obtained after screening additional cDNA melanoma libraries, were found to be approximately 2.5 kb in length. In vitro translation and transient transfection experiments indicated that MAGE-10 codes for a protein of approximately 72 kDa. This product was recognized by MAb 6C1 as well as by a polyclonal serum raised against a MAGE-10 peptide, thus demonstrating its identity with MAGE-10. Analysis of MAGE-10 mRNA by RT-PCR confirmed its presence in testis and placenta but not in other normal tissues. Expression of MAGE-10 in melanoma tumors was found to parallel that of MAGE-1. Western blot analysis with the polyclonal anti-MAGE-10 antibody showed the presence of MAGE-10 in lysates of purified trophoblast cells. Immuno-cytochemistry of cultured melanoma cells indicated that MAGE-10 is a nuclear protein.

Nitric oxide enhances the manganese superoxide dismutase-dependent suppression of proliferation in HT-1080 fibrosarcoma cells

The overexpression of manganese superoxide dismutase (MnSOD), an enzyme that catalyzes the removal of superoxide (O2*-) from the mitochondria, has been shown to be closely associated with tumor regression in vivo and loss of the malignant phenotype in vitro. To investigate the mechanism by which MnSOD overexpression mediates this reversal, we have established 29 independent, clonal MnSOD-overexpressing HT-1080 fibrosarcoma cells. MnSOD activity is inversely correlated with cell proliferation in our cell lines. Incubating cells in 3% oxygen can prevent the inhibition of cellular proliferation mediated by MnSOD, suggesting that oxygen is a prerequisite component of the MnSOD-dependent proliferative inhibition. Confocal laser microscopy was used in combination with the oxidant-sensitive fluorescent dyes dihydrorhodamine-123, dihydroethidium, and 2',7'-dichlorodihydrofluorescein diacetate to determine the oxidizing capacity of the MnSOD-overexpressing cells. When compared with parental or control cell lines, there was a significant decrease in the rate of oxidation of the fluorophores in the MnSOD-overexpressing cell lines. Thus, an increase in the oxidizing capacity of the cells does not appear to mediate the inhibition of proliferation associated with MnSOD overexpression. Superoxide dismutase has also been shown to enhance the cytotoxic activity of NO* toward tumor cells. In this study, we have shown that MnSOD overexpression enhances the cytostatic action of the NO* donors, sodium nitroprusside, 3-morpholinosydnonomine, and (Z)-1-[2-aminethyl)-N-(2-ammonioethyl)amino]diazen-1-+ ++ium-1,2-diolate in a dose-dependent manner. In addition, the NO* toxicity is blocked by oxyhemoglobin, a NO* scavenger. Our findings suggest that NO* may play a role in the reversal of tumorigenicity associated with MnSOD overexpression.

Genetic and molecular analysis of cglB, a gene essential for single-cell gliding in Myxococcus xanthus

Gliding movements of individual isolated Myxococcus xanthus cells depend on the genes of the A-motility system (agl and cgl genes). Mutants carrying defects in those genes are unable to translocate as isolated cells on solid surfaces. The motility defect of cgl mutants can be transiently restored to wild type by extracellular complementation upon mixing mutant cells with wild-type or other motility mutant cells. To develop a molecular understanding of the function of a Cgl protein in gliding motility, we cloned the cglB wild-type allele by genetic complementation of the mutant phenotype. The nucleotide sequence of a 2.85-kb fragment was determined and shown to encode two complete open reading frames. The CglB protein was determined to be a 416-amino-acid putative lipoprotein with an unusually high cysteine content. The CglB antigen localized to the membrane fraction. The swarming and gliding defects of a constructed DeltacglB mutant were fully restored upon complementation with the cglB wild-type allele. Experiments with a cglB allele encoding a CglB protein with a polyhistidine tag at the C terminus showed that this allele also promoted wild-type levels of swarming and single-cell gliding, but was unable to stimulate DeltacglB cells to move. Possible functions of CglB as a mechanical component or as a signal protein in single cell gliding are discussed.

Analysis of a Streptomyces antibioticus chromosomal region involved in oleandomycin biosynthesis, which encodes two glycosyltransferases responsible for glycosylation of the macrolactone ring

A 6-kb region from the chromosome of Streptomyces antibioticus, an oleandomycin producer, was cloned and sequenced. This region was located between the 3' end of the gene encoding the third subunit of the oleandomycin type I polyketide synthase and the oleP and oleB genes, which encode a cytochrome P450 monooxygenase and an oleandomycin resistance gene, respectively. Analysis of the nucleotide sequence revealed the presence of five genes encoding a cytochrome P450-like protein (oleP1), two glycosyltransferases (oleG1 and oleG2) involved in the transfer of the two 6-deoxysugars (L-oleandrose and D-desosamine) to the oleandomycin macrolactone ring, a methyltransferase (oleM1), and a gene (oleY) of unknown function. Insertional inactivation of this region by gene disruption generated an oleandomycin non-producing mutant which accumulated a compound that, according to mass spectrometry analysis, could correspond to the oleandomycin macrolactone ring (oleandolide), suggesting that the mutation affects oleandrosyl glycosyltransferase.

Absence of imprinting of HLA class Ia genes leads to co-expression of biparental alleles on term human trophoblast cells upon IFN-gamma induction

Human trophoblast cells have developed various efficient regulatory mechanisms to prevent cell surface expression of the classical HLA-A, -B, and (but not always) -C class I molecules. This allows them to escape maternal alloimmune attack during pregnancy. However, recent results have demonstrated that such a lack of expression could be reversed in villous cytotrophoblast cells purified from term placenta by in vitro IFN-gamma treatment. In this context, we investigated whether both maternal and paternal HLA class Ia antigens were co-dominantly expressed in such trophoblast cells. Using polymerase chain reaction sequence-specific primers for HLA-A and HLA-C alleles, we detected transcripts of both paternal and maternal origins, showing that these genes were not affected by genomic imprinting, at least in term placenta. After in vitro IFN-gamma treatment, the polymorphic HLA-A and HLA-B antigens of both parental origins become detectable at the cell surface, as assessed by flow cytometry and/or complement-dependent microtoxicity test. Appearance of paternal antigens on trophoblast cells upon IFN-gamma induction raises the question of the in vivo biological consequences of this phenomena, in term of materno-fetal tolerance and in particular of a potential allogeneic cytotoxic immune response.

Mandibular widening by intraoral distraction osteogenesis

Transverse mandibular deficiency with crowding of the mandibular anterior teeth is frequently present in patients with Class I and II malocclusions. The hallmarks of treatment by compensating orthodontics, functional appliances or orthopaedic devices are instability, compromised periodontium and compromised facial aesthetics. A new surgical technique has been developed to widen the mandible. The method is based upon gradual osteodistraction following vertical interdental symphyseal osteotomy. Ten patients with transverse mandibular deficiency and significant dental crowding were treated by symphyseal distraction and subsequent non-extraction decompensating orthodontic treatment. Either an intraoral tooth-borne Hyrax appliance or a new custom-made bone-borne osteodistractor was used to gradually widen the mandible. The surgical procedures were accomplished under local anaesthesia and intravenous sedation in an ambulatory surgical setting using an individualized distraction protocol. The appliances were activated 7 days after symphyseal osteotomies, once each day at a rate of 1 mm per day and stabilized for 30-40 days after distraction. After the segments were distracted, non-extraction orthodontic alignment of the mandibular anterior teeth was accomplished. The symphyseal distraction gaps were bridged by new bony regenerate. Distraction osteogenesis provided an efficient surgical alternative to orthognathic surgery for widening the mandible and treatment of transverse mandibular deficiency without extraction of teeth.

Identification, localization, and expression of two novel human genes similar to deoxyribonuclease I

Two novel cDNAs, DNAS1L2 and DNAS1L3, are predicted to encode proteins of 299 and 305 amino acids with 56 and 46% residue identity (71 and 63% similarity), respectively, to deoxyribonuclease I (DNase I). DNAS1L2 is located on a 16p13.3 cosmid, while DNAS1L3 maps to 3p14.3-p21.1 by fluorescence in situ hybridization and by PCR analysis of a radiation hybrid panel. Northern analysis revealed DNAS1L3 expression nearly exclusively in liver, while DNAS1L2 expression was detected in brain by RT-PCR. The previously defined DNL1L or DNAS1L1 is expressed highest in heart and skeletal muscle, while DNase I is expressed in the pancreas, parotid gland, and kidney. Thus, to date, four DNase I-like genes that show different tissue expression patterns are known. A comparison of DNAS1L1, DNAS1L2, and DNAS1L3 with the well-characterized DNase I suggests that the DNAS1L proteins are unlikely to be glycosylated or bind actin; however, catalytic and calcium- and DNA-binding residues are conserved, and potentially cleavable signal peptides are present among all these proteins. This analysis also identifies regions of high conservation among these proteins with no currently assigned function.

Interferon-gamma rescues HLA class Ia cell surface expression in term villous trophoblast cells by inducing synthesis of TAP proteins

Human placental trophoblast cells that constitute the materno-fetal interface during pregnancy escape maternal alloimmune attack. The different trophoblast cell subpopulations have developed efficient regulatory mechanisms to prevent expression of beta2-microglobulin-associated HLA class Ia molecules at their cell surface. We previously reported the presence of HLA class Ia messages in villous cytotrophoblast cells and in the syncytiotrophoblast differentiated in vitro purified from term placenta. In this study, we found that these transcripts are translated in heavy chain proteins that are endoglycosidase H sensitive and thus retained in the endoplasmic reticulum or cis-Golgi. Moreover, these class Ia heavy chains can be co-immunoprecipitated with the chaperone protein calnexin resident in the endoplasmic reticulum. When these trophoblast cells are treated with interferon (IFN)-gamma, part of the class Ia heavy chains become endoglycosidase H resistant, demonstrating that they have left the endoplasmic reticulum. Furthermore, after such a treatment, these heavy chains are detectable at the cell surface of these trophoblast cells, as assessed by two-color flow cytometry analysis and immunoprecipitation of cell surface biotinylated proteins using the W6/32 anti-HLA class I monoclonal antibody (mAb). IFN-gamma treatment induces a significant enhancement of the transcription of transporters associated with antigen processing (TAP1 and TAP2) rather than an increase of HLA class I or beta2-microglobulin messages. Finally, we demonstrate that an anti-TAP1 mAb co-immunoprecipitates TAP1 proteins and HLA class Ia heavy chains in these IFN-gamma-treated trophoblast cells. Thus, the constitutive absence of HLA class Ia cell surface expression in term villous cytotrophoblast and syncytiotrophoblast is likely to be due to a lack of transporter proteins that participate in the proper assembly of these molecules in the endoplasmic reticulum. Such a defect can be modified upon IFN-gamma treatment.

A gene similar to PKD1 maps to chromosome 4q22: a candidate gene for PKD2

We report a partial cDNA sequence that encodes a protein, dubbed "polycystwin," with 21% identify and 46% similarity to amino acids 3688-4109 of the carboxyl terminus of polycystin, the gene product of the autosomal dominant polycystic kidney disease locus located on chromosome 16 at band p13 (PKD1). Northern analysis demonstrates that the R48321 gene is expressed in all tissues examined, including both adult and fetal kidneys. Finally, in situ hybridization studies localize this novel gene to 4q22, where PKD2, the second most common locus for ADPKD, is known to map. Therefore, R48321 is an excellent candidate gene for PKD2.

Topological studies of the membrane component of the OleC ABC transporter involved in oleandomycin resistance in Streptomyces antibioticus

The OleC ABC transporter of Streptomyces antibioticus is constituted by an ATP-binding protein (OleC) and a hydrophobic protein (OleC5). Here we present experimental evidence demonstrating that the OleC5 protein is an integral membrane protein and we propose a topological model for its integration into the membrane. This model is based on the generation of hybrid proteins between different regions of OleC5 and a Escherichia coli beta-lactamase (BlaM) and the determination of the minimal inhibitory concentrations to ampicillin in these constructions. Fusions were generated both by cloning specific fragments of oleC5 and by creating ExoIII nested deletions of the gene. In the topological model proposed there will be six alpha-helix transmembrane regions, two cytoplasmic and four periplasmic loops and a hydrophobic linker domain.

Effectiveness of a whole cell pertussis vaccine in child-care centers and schools

BACKGROUND

Pertussis has substantially increased in Quebec, Canada, since 1990. We estimated pertussis vaccine effectiveness and vaccine coverage in child-care centers and elementary schools.

METHODS

Two retrospective cohort studies were simultaneously conducted. One included 4482 children attending 88 public child-care centers and the other included 3429 pupils in 14 elementary schools. Cough and pertussis symptoms were assessed through a questionnaire and medical records; immunization status was ascertained by examination of written records.

RESULTS

In child-care centers 95% of children had received at least three vaccine doses at the beginning of the follow-up; in schools more than 98% of pupils had received at least 4 doses. With > or = 4 doses of vaccine and a standard case definition used for surveillance (cough > or = 2 weeks, > or = 1 pertussis symptom and no other apparent cause for cough), vaccine effectiveness was estimated at 61% (95% confidence interval, 44 to 72%) in child-care centers and at 60% (95% confidence interval, 10 to 82%) in schools. With the same number of doses but a case definition requiring a cough > or = 5 weeks, vaccine effectiveness increased to 71% (95% confidence interval, 49 to 83) in child-care centers and to 86% (95% confidence interval, 66 to 94%) in schools.

CONCLUSIONS

The increase in pertussis in Quebec is not caused by a low vaccine coverage. A low vaccine effectiveness may contribute to the resurgence of pertussis in the past decade.

Somatostatin antisense oligodeoxynucleotide-mediated stimulation of lymphocyte proliferation in culture

We have previously shown that somatostatin (SRIF) is synthesized in B and T lymphocytes of rat spleen and thymus and released into the medium of cultured lymphocytes. To determine the role of SRIF in the control of lymphocytes proliferation, the expression of SRIF in normal lymphocytes was inhibited using a 3'-terminal phosphorothioate-modified antisense oligonucleotide complementary to a sequence that includes the translation start site of the rat SRIF messenger RNA. Spleens were obtained from adult male rats, and their lymphocytes were cultured for 24 or 72 h to measure SRIF content and cell proliferation, respectively. For the proliferation studies, [3H]thymidine was incorporated during the final 18 h. The lymphocytes were incubated with 15-30 micrograms/ml SRIF antisense and control antisense. SRIF antisense (25 micrograms/ml) increased lymphocyte proliferation 15-fold (P < or = 0.001), reaching a plateau (25- to 30-fold increase) between 25-30 micrograms/ml SRIF antisense. SRIF was extracted from lymphocytes and measured by RIA. Levels of SRIF content were almost undetectable with 10 micrograms/ml antisense and were significantly lower (P < or = 0.01) with 25 micrograms/ml antisense. When RC 160 (10(-5) M), a SRIF agonist analog, was used in the incubation, the stimulation of cell proliferation exerted by the SRIF antisense was completely abolished. Control antisense had no effect on proliferation or SRIF content. These findings indicate that 1) lymphocytes in culture are able to incorporate SRIF antisense; and 2) SRIF antisense inhibits the expression of lymphocytic SRIF, which leads to lymphocyte proliferation. In conclusion, cell proliferation is dramatically increased by eliminating the expression of SRIF from the lymphocytes, which indicates that in vitro SRIF is acting in a paracrine and/or autocrine fashion to inhibit lymphocyte proliferation.

Placental expression of HLA class I genes

This article presents an overview of the more recent data dealing with the constitutive, transcriptional, and translational expression of classical class Ia and nonclassical HLA-E and -G class Ib products in the different trophoblast cell subpopulations that constitute the maternofetal interface during human pregnancy. Of particular interest is the expression of alternatively spliced HLA-G transcriptional isoforms that may be translated in membrane-bound or soluble protein products. Molecular regulatory mechanisms that may control the differential expression of class Ia and class Ib molecules, according to the cell types, state of differentiation, and stages of gestation are also examined. They may operate at the levels of transcription, translation and/or transport of proteins to the cell surface. Functional significance of the absence of detectable cell surface expression of class Ia molecules in all trophoblast cell subpopulations, and of the presence of membrane-bound HLA-G products in extravillous cytotrophoblast cells is finally questioned.

Detection of membrane-bound HLA-G translated products with a specific monoclonal antibody

A monomorphic anti-HLA-G monoclonal antibody (mAb) was obtained by immunization of HLA-B27/human beta 2-microglobulin double-transgenic mice with transfected murine L cells expressing both HLA-G and human beta 2-microglobulin. This mAb, designated BFL.1, specifically recognizes, by flow cytometry analysis, the immunizing HLA-G-expressing cells, whereas it does not bind to parental untransfected or to HLA-B7- and HLA-A3-transfected L cells, suggesting that it distinguishes between classical HLA-A and -B and nonclassical HLA-G class I molecules. This was further assessed by the absence of BFL.1 reactivity with a number of human cell lines known to express classical HLA class I proteins. In addition, we showed that the BFL.1 mAb also labels HLA-G-naturally-expressing JEG-3 and HLA-G-transfected JAR human choriocarcinoma cell lines as well as a subpopulation of first-trimester placental cytotrophoblast cells. Further biochemical studies were performed by immunoprecipitation of biotinylated membrane lysates: BFL.1, like the monomorphic W6/32 mAb, immunoprecipitated a 39-kDa protein in HLA-G-expressing cell lines, a size corresponding to the predicted full-length HLA-G1 isoform. However, in contrast to W6/32, which immunoprecipitates both classical and nonclassical HLA class I heavy chains, BFL.1 mAb does not recognize the class Ia products. Such a mAb should be a useful tool for analysis of HLA-G protein expression in various normal and pathological human tissues and for determination of the function(s) of translated HLA-G products.

Methylation status and transcriptional expression of the MHC class I loci in human trophoblast cells from term placenta

Of the various molecular regulatory mechanisms that may be used by human trophoblast cells to down-regulate expression of HLA class I genes, we chose to investigate the methylation of DNA, generally associated with inhibition of transcription. We analyzed the methylation status of different HLA class I loci in villous and extravillous cytotrophoblast cells and in vitro-differentiated syncytiotrophoblast, purified from human term placenta, as well as in the human trophoblast-derived JAR and JEG-3 cell lines. We then compared methylation status and transcriptional activity. An inverse relationship was established between JAR and JEG-3: HLA-A, -B, and -G are methylated and repressed in JAR, whereas in JEG-3, HLA-A is methylated and repressed but HLA-B and -G are partially methylated and transcribed. HLA-E is unmethylated and transcribed in both cell lines. Apart from HLA-E, which is always unmethylated and transcribed, no such relationship exists for the other class I loci in trophoblast cells. Whereas nonclassical HLA-G and classical HLA-A and -B class I genes are undermethylated in both cytotrophoblast and syncytiotrophoblast, they are clearly transcribed in the former but minimally transcribed in the latter subpopulation. Thus, the down-regulation of class I gene expression in the in vitro-differentiated syncytiotrophoblast is unlikely to be caused by DNA methylation. Furthermore, there is no detectable expression of any class I molecule at the cell surface of either trophoblast cell subpopulation, suggesting a negative control on translation and/or on the secretory pathway to the plasma membrane.

Methylation status and transcriptional expression of the MHC class I loci in human trophoblast cells from term placenta

Of the various molecular regulatory mechanisms that may be used by human trophoblast cells to down-regulate expression of HLA class I genes, we chose to investigate the methylation of DNA, generally associated with inhibition of transcription. We analyzed the methylation status of different HLA class I loci in villous and extravillous cytotrophoblast cells and in vitro-differentiated syncytiotrophoblast, purified from human term placenta, as well as in the human trophoblast-derived JAR and JEG-3 cell lines. We then compared methylation status and transcriptional activity. An inverse relationship was established between JAR and JEG-3: HLA-A, -B, and -G are methylated and repressed in JAR, whereas in JEG-3, HLA-A is methylated and repressed but HLA-B and -G are partially methylated and transcribed. HLA-E is unmethylated and transcribed in both cell lines. Apart from HLA-E, which is always unmethylated and transcribed, no such relationship exists for the other class I loci in trophoblast cells. Whereas nonclassical HLA-G and classical HLA-A and -B class I genes are undermethylated in both cytotrophoblast and syncytiotrophoblast, they are clearly transcribed in the former but minimally transcribed in the latter subpopulation. Thus, the down-regulation of class I gene expression in the in vitro-differentiated syncytiotrophoblast is unlikely to be caused by DNA methylation. Furthermore, there is no detectable expression of any class I molecule at the cell surface of either trophoblast cell subpopulation, suggesting a negative control on translation and/or on the secretory pathway to the plasma membrane.

A cytochrome P450-like gene possibly involved in oleandomycin biosynthesis by Streptomyces antibioticus

A cosmid clone from an oleandomycin producer, Streptomyces antibioticus, contains a large open reading frame encoding a type I polyketide synthase subunit and an oleandomycin resistance gene (oleB). Sequencing of a 1.4-kb DNA fragment adjacent to oleB revealed the existence of an open reading frame (oleP) encoding a protein similar to several cytochrome P450 monooxygenases from different sources, including the products of the eryF and eryK genes from Saccharopolyspora erythraea that participate in erythromycin biosynthesis. The oleP gene was expressed in Escherichia coli as a fusion protein to a maltose-binding protein. Using polyclonal antibodies against this fusion protein it was observed that the synthesis of the cytochrome P450 was in parallel to that of oleandomycin. The cytochrome P450 encoded by the oleP gene could be responsible for the epoxidation of carbon 8 of the oleandomycin lactone ring.

Adhesive properties of choriocarcinoma cells toward lymphocytes activated or not by interleukin-2

Choriocarcinoma cells (CC) in vitro are resistant to NK lysis but sensitive to lysis by blood or decidual effectors activated by interleukin-2 (IL-2). Because lytic activity requires a step of adhesion, the adhesive properties of the choriocarcinoma cells BeWo, JEG-3, and JAR were examined functionally toward peripheral blood lymphocytes. The adhesion of lymphocytes to choriocarcinoma cells was very low and did not increase after stimulating lymphocytes with IL-2. As demonstrated by cytofluorimetry analysis, choriocarcinoma cells and cytotrophoblast cells prepared from term placenta expressed intercellular adhesion molecule-1 (ICAM-1), whereas only CC expressed CD56. Tumor necrosis factor-alpha or interferon-gamma increased the expression of ICAM-1 on choriocarcinoma cells without modifying the adhesion of lymphocytes to choriocarcinoma cells. These results suggest that resistance of choriocarcinoma cells to lysis by cytotoxic effectors could partially be attributed to the low level of lymphocyte adhesion to these cells.

Cantilever and implant biomechanics: a review of the literature, Part 2

In Part 2 of this literature review, a summary of the literature regarding the determination of acceptable cantilever lengths for fixed implant prostheses is presented. Studies examining the possible effects of biomechanical stress on both the implant prosthesis and the supporting bone are also discussed.